Roasting sulphur-bearing materials, etc.



Mar. 6, 1923.

\ 1,447,645. M. F. CHASE ET AL ROASTING SULPHUR BEARING MATERIALS, ETC FILED MAY 1, I919- 2 SHEETS-SHEET IIWENTORS Era. WWky Arrow Mar. 6, 1923. 1,447,645. M. F. CHASE ET AL ROASTING SULPHUR BEARING MATERIALS, ETC.

FILED MAY 1| 1919- 2 SHEETS-SHEET 2.

mum/5 2 2 I MlVf/WW/f ram Patented Mar. 6, 1923.

A t at MARCH F. CHASE, OF CIiEVELAlfTD, OHIO, AND FREDERIC E. AND JOHN 'SKOGMARK, OF NEW YORK, N. Y.,'.ASSIG1\TORS TO THE COS PROCESS COMPANY,

INC OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ROASTING SULPHUR-BEARING MATERIALS, ETC.

Application filed May 1, 1919. Serial No. 294,065.

To all whom it may concern Be it known that we, MARCH F. CHASE and FREDERIC E. PIERCE, both citizens of the United States, residing, respectively, said CHASE at Cleveland, Ohio, and said PIERCE at New York city, N- Y., and JOHN SKOG- MARK, a subject of the King of Sweden, residing at New Yorkcity, N. Y.,-have 1nvented the following described Improvements in Roasting Sulphur-Bearing Materials, Etc. v Sulphur dioxide (80,) is produced in the process of roasting sulphide ores of z nc, iron, copper etc., burning sulphur as br mstone or from any sulphur bearing mater als and is used subsequently as a gas in processes by which the said SO may be converted into. elementalv sul hur (S) liquid S0,, sulphurous acid (H 0 or a water solution of the same, sulphuric acid (11 80,) either in a diluted form or as sulphuric anhydrid (S0,) or combinations for uses in the arts.

Roasting of the sulphide ores mentioned is a necessary operation because it has not been found generally possible to smelt or otherwise treat metallurgically these ores until almost free of their sulphur content.

The process of roasting such ores, as usually carried on, consists 'in burning oil the sulphur, which is accomplished in furnaces or burners of several well known types. In. these, the ores, brought up to the temperature of ignition by the heat in the burner gases, are rabbled mechanically continuously or intermittently or otherwise stirred and gradually made' to pass through the furnace or burner, the sulphur, burning ofi meanwhile, deriving the oxygen necessary for the combustion from the air admitted 1n proper quantity! through adjustable open in in the furnace or burner. The product of the combustion of the sulphur, S0,, mixes with the uncombined oxygen in the admitted air, the nitrogen and other constituents present and forms the burner gases referred to above. The percentage of SO by volume in these gases ordinarily varies between 5% and 7%, but it may be quite low, 1% or 2%, and under certain conditions quite high, 14% or 15%. Inv any event the strength of the gas is limited by the per cent of oxygen in the air. As it is desirable in some operations to have burner gases very rich in S0, and to have the percentage of SO under control,

it is one object: of this invention to bring this about.

As 'the ore passes through the furnace, the

sulphur burning-off the' while, the sulphur content is gradually reduced until such time as it is discharged from the furnace when its content of sulphur, in the case of iron ore may be as low as 1% or even less. Such a roasted ore is said to be dead or-sweet roasted. Dead roasted iron or zinc ores are very necessary for satisfactory metallurgical operations such as smelting them to obtain the metals. With copper and lead ores the dead roast with present metallurgical practice is not essential. The character of the ore, whether easily roasted or roasted with difliculty determines more or less the possi- No way has yet been discovered to successfully use this heat in a. continuously rabbled furnace without mixing the coal gases with the burner gases, which is highly objectionable if the S0 is tofbe used subsequently for the manufacture of liquid SQ, or Hl ,SO,,. Besides these there areother objections such as additional, equipment, extra labor, etc. Further objects of this invention are to do away with this extra fuel and at the same time produce the dead roasted ore, which will be explained presently. t

The heat units generated by burning the sulphur in ores commonly treated are theoretically sufficient to roast the ore, if elliciently applied, even after-reasonable a1- lowances are made for radiation, but there are other more serious losses. The main bility of producing a dead roast without ones are, 1st, radiation; 2nd, that carried j away in the hot burner gases; 3rd, that lost in the hot roasted ore discharged from the furnace. The first can be somewhat controlled but there will be art-unavoidable loss on this account even' if reduced to a minimum. The third is ifmwfi-idahle but is not very'great and may be recovered in ore coolers so designed as to preheat the air admitted to the furnace. The second due to the great volume of the burner gases makes for .the most' considerable loss, although some of this may be reclaimed in a suitable air-heater. Further objects of this invention are to' control the unavoidable losses and reduce them to ininimaand to greatly limit the loss due to the large volume of the burner gases by reducing this volume.

In place of air the process employs oxygen gas or gas mixture with a higher content of oxygen than ordinary air as the principal source of oxygen-for burning the sulphur. In such a gas'mixture the percentage of nitrogen and other inert gases in air may be exceedingly small and in any case will be less than in ordinary air. Thus the high content of SO in the gases may be obtained by burning the orein a furnace in which the gas mixture rich in oxygen is admitted' It is evident that the use of such a, gas mixture may produce I temperatures in the furnace greatly in excess of those ordinarily encountered in metallurgical work and the usual construction of such furnaces might not stand up under the conditions then brought about, unless the combustion is under nice re lationand complete control.

, his invention relates to such regulation and complete control as applied generally to such a process and in particular to the with it, a blower to propel the gas, and if special applications of the same for the dead roasting of zinc and iron ores and for the. burning of brimstone.

The process is as follows A volume of gas containing any desired percentage of. S0 is made to circulate in a system made up of apparatus such as the furnace or burner, a dust catcher, if necessary, following the burner, a gas cooler, which maybe the dustcatcher or combined the dust catcher, if'used, or the gas cooler,

an equivalent amount of burner gases, now with SO replacing'the oxygen to the extent desired is withdrawn from the system .bya blower. or other suitable means for the purposes as" previously stated, viz :--for conversion into elemental sulphur, liquid S0,, sulphurous acid, sulphuric acid or sulphuric anhydrid, etc.-

By'varying the volume of gas circulated.

the temperature of the furnace or burner can be regulated and the rate of burning the sulphur controlled. This regulation of the vplume of the gas circulated is effected by the by-pass of the blower, which consists of a pipe with a valve in it.- By opening or closing this valve the amount of gas circulated. by the blower can be cont-rolled to a nicety. The regulation can also be accomplished by using a fan type blower with a valve in the pipe.

The oxygensupply is connected up with the blower in such a way as to shut it off in case the blower stops accidentally or otherwise.

The rate at which the oxygen supply is admitted depends on the amount withdrawn at theexit and an automatic control is installed between the blower and the oxygen supply regulating the amount admitted, such automatic control being of several types and well'known.

This system of apparatus and pipes would also have the necessary valves, measuring instruments for temperatures and pressures, machines to automatically analyze the gases and such other appliances ordinarily used in such combinations and is not in any way limited to the exact parts mentioned which are cited. as the principal elements for the purpose of a clear description.

The diagram Fig. 1, shows the system consisting of the. furnace or burner (1) the gas cooler (2), the blower (3), the by:pass of the blower (4), the connecting piping (5), the ,oxy en supply (6) the exit (7), various valves g8) measuring instruments for temperatures (9), for pressures (10), for flow of gases (11), automatic connection between exit blower and oxygen supply for control of the latter (12), emergency shut off for oxygen supply (13). Such a system is adapted to the burning of sulphur or brimstone. 4

The diagram Fig. 2 shows a variation of a part of the system in diagram Fig. 1 in that, part of the oxygen supply is introduced directly into the lower hearths of the furnace. The reason for this 'is to bring about a more active combustion in that part of the furnace where the sulphur content of the ore has been reduced to 5% or less and thus reduce it to the minimum without bringing it in contact with gases with a high special application it is sometimes desirable to return the circulating gas enriched with oxygen at more than one point on one hearth oron several hearths'and this also applies to the introduction of the oxygen gas or gas mixture with the high content of oxygen 4 which may be introduced at several points operation which hasbeen described.

In-roasting zinc or iron ores part of the oxygen introduced .in the furnace is used to oxydize themetals and part of'it used for burning the sulphur which is of course also an oxidation. reaction. A In this case more oxygen is introduced in the system than is removed inthe exit .and a relation. has to beestablished between them. This depends-- on the character of the ore and the analyses of the gases and the volume circulated. Means for makin this adjustment rests in the speed of the b ower on the exit which is under'control, and the connection between this blower and the oxygen supply.

, In burning sulphur in the form of brimstone which is almost pure sulphur, practically all of the oxygenvadmitted unites with the sulphur to form S0 and the volume introduced,-barrin'g leaks in the apparatus and the small percentages of impurities in' the brimstone which may require a small amount ofkoxygen, would be the same as the volume withdrawn at .the exit-reduced of course to the standard temperature of 0 C. which is used in calculating as volumes.

, vThe foregoing operations t lnis bring about two general classes; first, where a consider- .able part of the oxygen is required for the oxidation of the ores and-the gas withdrawn at the exit is considerably less than that introduced as'the oxygen supply, and second, where the volume of gas withdrawn is practically the same as the volume from the oxygen supply admitted tothe furnace.

The following two examples will serve to I explain this in more detailf In a zinc roasting furnace suppose the volume of gas circulatingis IOOO-cu. ft. (reduced to 0? C.) then the volume from the oxygen supply admitted to it just before it enters the furn'ace, or, mixed with it inside the furnace, might be 700 cu. ft., making a total of 1700 cu. ft. In the furnace we will leaving sup-pose the ores requirethe oxygen equivalent to 200 cu. ft. of this gas, then'the gas the furnace would. have a volume of 1500 cu. ft. but this would have the desired analysis of the circulating volume. .Of this,

500 cu ft. is withdrawn at the exit and the balance of 1000 cu. returns to the blower and goes through the cycle again. The diagram Fi 3, shows thls condition theoreti-' cally an the complete cycle. In practice there would be some variations from this from time to.

time but the means fofadjusting these vari- -ations has already been explained and by all that can be said about this except that it will be noted that the Isame volume of gas (reduced to 0 (1-)... is withdrawn at the exit as is admitted from the oxygen supply.

Comparison of these two examples will also show that in roasting ore a gas mixture is introduced in the furnace having a reference to it will show clearly high percentage of oxygen for the purpose of obtaining more rapid combustion and higher temperature to roast the ores more efiectively.

These examples are selected more or less at random and are cited to show the wide variations that may be brought about to,

suit the conditions which-may have to be i met.

To be more specific the point is that this process serves to control the rate of com bustion in and otherwise regulate the furnace or burner and to improve the practice over what has formerly been possible both in obtaining rich SO, gas and producing dead or sweet roasted ores and it is to be construed broadly and not limited in any way by the diagrams, which are purely for explanation purposes.

The furnace or burner herein referred to may be of the general type illustrated for example in Patent No. 916,234, or any equivalent structure.

Having thus described our process, wenew claim the same as follows:--

1. A method of roasting sulphur-bearing ores of zinc, iron, copper, etc., which con-. sists in circulating a gas mixture-consist ing mainly ofsulphur dioxide, oxygen and nitrogen through a furnace and in contact with the ore therein, introducing. oxygen to establish in the furnace a reactive medium; of greater oxygen content than air,

abstracting a relative portion of the mixture from the circulation and controlling the temperature of the gases circulated; 2. A method of roasting sulphur-bearing ores of zinc, iron, copper, etc.,- which consists in circulating a gas mixture consisting mainly of sulphur dioxide, oxygen and nitrogen'through a closed system including a furnace, admitting said mixture to the furnace at different points, introducing oxygen to maintain in the furnace a reactive the mixture from the system.

3. A method of roasting sulphur-bearing ores which consists in circulating a gas mixture consisting mainly of sulphur dioxide, oxygen and nitrogen through a closed system including a mutiple-hearth furnace, admitting the same to different hearths of said furnace and introducing oxygen to one of said hearths to establish therein a reactive medium of greater oxygen content than air.

4. A method of roasting sulphur-bearing ores of zinc, iron, copper, etc. which consists in circulating a gas mixture consisting of sulphur dioxide, oxygen and diluent gases, through a closed system including the upper hearths of a multiple hearth furnace, introducing a gas rich in oxygen to the lower of said hearths to establish therein a reactive medium of'higher oxygen content than air, abstracting from the circulation a relative portion of the increased volume, and controlling the temperature of the gases circulated.

5. The method of roasting sulphide ores or sulphur-bearing materials which consists in passing a current of gas with a higher oxygen content than air through a combustion chamber in contact with said materials, and varyin the oxygen content of said gas to control t e temperature of said chamber and at the same time producing a gas with a high SO content.

.6. The method of roastingsulphur-bearing materials which consists in passing a current of gas with a higher oxygen content than alr through a combustion chamber in contact with said materials and controlling the temperature in the combustion chamber by varying the flow therethrough.

7. The method of roasting sulphur-bear ing materials which consists in passing a current of gas with a higher oxygen content than air in' contact with a counter current of said materials and maintaining a predetermined temperature condition in the current of said materials by varying the oxygen content of said gas.

8. The method ofroasting sulphur-bearing materials which consists in passing a current of gas with a higher oxygen content than air 'in contact with a counter current of said materials and maintaining a predetermined sulphur content of the material by varying the oxygen content of said stream of said ore in a suitable furnace, in-- troducingoxygen so as to establish a reactive medium of higher oxygen content than air in the part of said furnace which is adjacent the point of ore discharge, abstracting a relative portion of the mixture from the circulation and controlling the temperature of the gases circulated.

10. A method of roasting sulphur-bearing ores which, consists in causing the ore to progress through a suitable furnace, circulating a gas mixture consisting mainly of sulphur dioxide, oxygen and diluent gas through a closed system including said furnace and in contact with said ore, introducing oxygen to the furnace near the point of ore discharge to establish therein a reactive medium of higher oxygen content than air and regulating the temperature of the furnace by controlling the rate of flow through the system.

11. Method of producing sulphur dioxid of high concentration, comprising preparing a gaseous mixture consisting essentially of sulphur dioxid and oxygen, and reacting therewith on a sulphur-bearing material.

12. Method of producing sulphur dioxid of high concentration, comprising reacting on a sulphur-bearin the oxygen content of the mixture being in excess of the oxygen content of atmospheric air.

material with a mixture containing sulp ur'dioxid and oxygen,

13. Method of producing sulphur dioxid 15. Method of producing sulphur dioxid of high concentration, comprising roasting a sulphur-bearing material and withdrawing the evolved gases; adding to a portion thereof suflicient oxygen to give an oxygen concentration approximating 40%; and returning the oxygen-containing portion of the gases to the roasting chamber.

16. Method of producing sulphur dioxid of high concentration, comprising roasting a sulphur-bearing material, withdrawing and cooling theevolved gases, adding to a portion thereof suificient oxygen to give an oxygen concentration in excess of that of atmospheric air, and returning the oxygencontaining mixture to the roasting chamber.

17. Method of producin sulphur dioxide of high concentration w ch consists in roasting a sulphur-bearing material in a oxygen through said furnace in contact with the ore, introducing oxygen to that part of 15 the furnace where the ore contains lessthan about 5% of sulphur to establish in said part. an oxygen concentration in excess of air, and regulating the furnace temperature by controlling the volume of gases passing 20 through the furnace.

In testimony whereof, we have signed'this specification.

MARCH F. CHASE. FREDERIC E. PIERCE. JOHN SKOGMARK. 

